Cleaning system for a continuous ink jet printer

Abstract

A cleaning system for a continuous ink jet printer includes a first solvent supply conduit connected to a solvent source for conveying solvent through a supply opening and onto the front face of the print head. A second solvent supply conduit is connected to the solvent source for conveying solvent through a supply opening and onto a surface of the catcher. The solvent that is supplied to the print head and the catcher is removed under vacuum and returned to the ink supply system. The cleaning system may include an orifice unclogging mechanism that causes said solvent disposed on said front face to flow into said orifice in the reverse of the direction ink flows through said orifice for printing. The cleaning system may also include a piezoelectric element for generating a stress wave in the print head during cleaning. The piezoelectric element may comprise a piezoelectric oscillator that is also used during printing to creates perturbations in the ink flow at the nozzle so as to generate a stream of spaced drops from the nozzle.

1. A cleaning system for a continuous ink jet printer of the type having an ink flow system in which ink is adapted to flow from a reservoir to a print head from which the ink is ejected in a series of discrete droplets directed at a substrate upon which an image is to be formed by applying droplets to the surface of the substrate and in which droplets which are not to be applied to the substrate are collected in a catcher and recycled via a return line to the ink flow system for reuse, the print head including a front face and at least one orifice extending through the front face, the orifice defining a nozzle for ejecting the ink, the cleaning system comprising:
 a source of solvent; 
 a first solvent supply conduit connected to the solvent source for conveying solvent through a supply opening and onto the front face of the print head; and 
 a second solvent supply conduit connected to the solvent source for conveying solvent through a supply opening and onto a surface of the catcher. 
 
   
   
     2. A cleaning system as set forth in  claim 1 , further comprising an orifice unclogging mechanism that causes said solvent disposed on said front face to flow into said orifice in the reverse of the direction ink flows through said orifice for printing. 
   
   
     3. A cleaning system as set forth in  claim 2 , wherein the printer further comprise a main conduit for supplying ink to said orifice, and wherein the orifice unclogging mechanism further includes a vacuum conduit connected to the main conduit so that negative pressure may be applied to suction solvent from the front face, through the orifice and into the vacuum conduit. 
   
   
     4. A cleaning system as set forth in  claim 3 , further comprising a check valve disposed in said vacuum conduit, the check valve being adapted to open to allow solvent to be suctioned through said vacuum conduit in a first direction and to close to prevent backflow through said conduit in the opposite direction. 
   
   
     5. A cleaning system as set forth in  claim 4 , wherein the check valve comprises an elastomeric member. 
   
   
     6. A cleaning system as set forth in  claim 1 , further comprising a piezoelectric element for generating a stress wave in the print head during cleaning. 
   
   
     7. A cleaning system as set forth in  claim 6 , wherein the piezoelectric element comprises a piezoelectric oscillator that is also used during printing to creates perturbations in the ink flow at the nozzle so as to generate a stream of spaced drops from the nozzle. 
   
   
     8. A cleaning systems as set forth in  claim 1 , further comprising a drain conduit for suctioning solvent from the front face of the print head. 
   
   
     9. A method of cleaning a continuous ink jet printer of the type having an ink flow system in which ink is adapted to flow from a reservoir to a print head from which the ink is ejected in a series of discrete droplets directed at a substrate upon which an image is to be formed by applying droplets to the surface of the substrate and in which droplets which are not to be applied to the substrate are collected in a catcher and recycled via a return line to the ink flow system for reuse, the print head having front face and at least one orifice extending through the front face, the cleaning method comprising the steps of:
 flowing solvent through a first solvent supply conduit to a front face of the print head such that the solvent moves along said front face adjacent to said orifice; 
 suctioning the solvent from the front face and into a drain conduit to remove said solvent from the front face of the print head; 
 flowing solvent through a second solvent supply conduit directly onto a surface of the catcher; and 
 suctioning the solvent from the catcher through the return line. 
 
   
   
     10. The method of  claim 9 , further comprising the step of flowing the solvent disposed on the front face of the print head into the orifice in the reverse of the direction ink flows through the orifice for printing. 
   
   
     11. The method of  claim 9 , further comprising generating a stress wave in the print head during the cleaning process. 
   
   
     12. The method of  claim 9 , further comprising operating a piezoelectric element of the print head during cleaning. 
   
   
     13. A method of cleaning a continuous ink jet printer of the type having print head with a front face presenting an orifice for emitting a droplet stream toward a substrate during a printing cycle, the cleaning method comprising the steps of:
 supplying solvent to a front face of the print head through a first solvent supply conduit such that the solvent moves along said front face adjacent to said orifice; 
 flowing solvent directly onto a surface of the catcher through a second solvent supply conduit; and 
 generating a stress wave in the print head during the cleaning process so as to loosen dried ink in the print head. 
 
   
   
     14. The method of  claim 13 , wherein the step of generating a stress wave comprising operating a piezoelectric element of the print head during cleaning. 
   
   
     15. The method of  claim 13 , further comprising
 suctioning the solvent from the catcher through a return line. 
 
   
   
     16. The method of  claim 13 , further comprising the step of flowing the solvent disposed on the front face of the print head into the orifice in the reverse of the direction ink flows through the orifice for printing. 
   
   
     17. A self-cleaning print head for an ink jet printer that directs ink to a substrate to be marked, the print head comprising:
 a drop generator having front face including an orifice for emitting a droplet stream toward a substrate during a printing cycle; 
 a charge electrode for selectively charging ink droplets in said droplet stream during the printing cycle; 
 a deflection plate and a ground plate having a channel formed therein, wherein an electrostatic field is formed between said deflection plate and said ground plate to deflect charged droplets of ink toward the substrate during the printing cycle; 
 a catcher for receiving uncharged droplets of ink during the printing cycle; and 
 a solvent supply system that supplies solvent directly to the front face of the drop generator through a first solvent supply conduit and to the catcher through a second solvent supply conduit during a cleaning cycle. 
 
   
   
     18. A self-cleaning print head for an ink jet printer that directs ink to a substrate to be marked, the print head comprising:
 a drop generator having an orifice for emitting a droplet stream toward a substrate during a printing cycle, the drop generator including a piezoelectric element that is operable during a cleaning cycle for generating a stress wave in the drop generator and that is operable during a printing cycle to create perturbations in the ink flow at the orifice so as to generate a stream of spaced drops from the orifice; 
 a solvent supply system that supplies solvent to the drop generator through a first solvent supply conduit to clean at least a portion of the drop generator during the cleaning process, said solvent supply system also supplying solvent to a catcher through a second solvent supply conduit, said solvent being formulated to remove ink residue from said drop generator as said solvent flows over said drop generator. 
 
   
   
     19. A print head as set forth in  claim 18 , wherein said solvent supply system supplies solvent to an exterior surface of the drop generator adjacent to the orifice. 
   
   
     20. A print head as set forth in  claim 18 , wherein the print head further comprises a catcher for catching uncharged ink drops during the printing cycle and wherein the solvent supply system further supplies solvent directly to a surface of said catcher during the cleaning process. 
   
   
     21. A cleaning system for a continuous ink jet printer having a print head including a front face and at least one orifice extending through the front face, the cleaning system comprising:
 a conduit for supplying solvent to the front face of the print head, adjacent the orifice; 
 a main ink conduit for supplying ink to said orifice; 
 a vacuum conduit connected to the main conduit so that negative pressure may be applied to suction solvent from the front face, through the orifice and into the vacuum conduit; and 
 a check valve disposed in said vacuum conduit, the check valve being adapted to open to allow solvent to be suctioned through said vacuum conduit in a first direction and to close to prevent backflow through said conduit in the opposite direction. 
 
   
   
     22. The cleaning system of  claim 21 , wherein the check valve comprises an elastomeric check valve.